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Awareness During Anesthesia

Awareness During Anesthesia. Do You Remember … ?. References . Awareness during anesthesia Anesthesiology Clinics of North America Volume 20 • Number 3 • September 2002 Awareness with recall during general anesthesia – Incidence and risk factors Anesth Analg 86: 1084-1089, 1998

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Awareness During Anesthesia

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  1. Awareness During Anesthesia Do You Remember…? Liu, Chih-Min

  2. References • Awareness during anesthesia • Anesthesiology Clinics of North America Volume 20 • Number 3 • September 2002 • Awareness with recall during general anesthesia – Incidence and risk factors • Anesth Analg 86: 1084-1089, 1998 • Awareness during anesthesia • Anethesiology 2000; 92: 597-602 • BIS Monitoring to Prevent Awareness during General Anesthesia • Anethesiology 2001; 94:520-2 • Awareness detected by auditory evoked potential monitoring • BJA 91 (2): 209-2 (2003) Liu, Chih-Min

  3. Before talking about it… • Did you ever forget anything…? • Patients are concerned that they would not be asleep during their surgery ( more then 50%) • For anesthesiologists, awareness under anesthesia ranks second only to death as a “dreaded” complication Liu, Chih-Min

  4. Definitions • Consciousness • ‘The state of being conscious; awareness of one’s own existence, sensation, thoughts, surroundings, etc’ • Awareness • ‘Having knowledge, conscious, cognizant’ Liu, Chih-Min

  5. General surgery 1960: 1.2% 2000: 0.11% to 0.16% Cardiac surgery 1977: 5.8% 1998: 0.3% Other types of surgery Major trauma High from 11% up to 43% Obstetric surgery (C/S) 1968: 11.8% 1991: 0.9% Incidence of awareness during anesthesia Liu, Chih-Min

  6. Patient perceptions of awareness • Most common • Sounds and conversation – 89%to 100% • Sensation of paralysis- 85% • Anxiety and panic • Helplessness and powerlessness • Pain- 39% • Least common • Visual perceptions • Intubation or tube • Feeling the operation without pain Liu, Chih-Min

  7. After-effects of Awareness During General Anesthesia • Mental after-effects • Muscle relaxation • Pain • Fear of dying • Medico-legal after-effects Liu, Chih-Min

  8. Mental after-effects • 37% of patients were responded with… • Disbelief • Ignorance • Anger • 14% of patients were told… • “just a bad dream” • “all in your imagination” • “were med or hallucinating” • “had a seventh sense” Liu, Chih-Min

  9. Then…there were • Sleep disturbances • fear when falling asleep • Repetitive nightmares • 52.4% • Anxiety and panic attacks • 55% • Depression • Flashbacks • Avoidance of medical care • Preoccupation of death • Post-traumatic stress disorder (PTSD) • 14.3% to 22% • From months (20m) to years (17y)! Liu, Chih-Min

  10. Medico-legal after-effects • Very large compensations… • USD 1,000 to 600,000 • Risk factors • No volatile agents used • Female • Obstetric or gynecology procedure • Opioid only • Muscle relaxant Liu, Chih-Min

  11. Causes of Awareness • Light anesthesia • Nitrous/opioid/relaxant anesthesia • Myocardial depression • Hypovolemia • Cesarean section • Difficult intubation • Premature discontinuation of anesthetic Liu, Chih-Min

  12. Causes of Awareness • Machine malfunction or misuse of technique • Failure to check equipment • Vaporizer and circuit leaks • Intravenous infusion errors • Accidental administration of muscle relaxant to awake patient Liu, Chih-Min

  13. Causes of Awareness • Increased anesthetic requirements • Variability in anesthetic requirements for intravenous agents • Increased anesthetic requirement because of chronic alcohol, opioid, and cocaine abuse Liu, Chih-Min

  14. Causes of Awareness Liu, Chih-Min

  15. Prevention of awareness • Administer amnestic premedicants. • Maintain vigilance regarding equipment and monitoring. • Minimize use of complete neuromuscular blockade. • Supplement nitrous/opiate anesthesia with a potent volatile anesthetic. • Maintain 0.8–1.0 MAC of a potent volatile anesthetic by itself. • Administer adequate dose of induction agent. • Obtain informed consent for high-risk patients. • Mask auditory input. • Provide education. • Monitor for awareness. Liu, Chih-Min

  16. Methods of detecting awareness • Postoperative interview • Structured • Best • Questions asked during interviews • What is the last thing you remember before going to sleep for the operation? • What is the first thing you remember after waking after the operation? • Do you remember anything in between? • Did you have any dreams? • What is the most unpleasant thing you remember from your operation and anesthesia? Liu, Chih-Min

  17. Methods of Monitoring Consciousness During General Anesthesia • Clinical signs • Sympathetic activities: HR, BP, sweating, pupillary dilatation, lacrimation … • Unreliable • Isolated forearm technique • EEG • BIS • AEP Liu, Chih-Min

  18. Awareness detected by auditory evoked potential monitoringBJA 91 (2): 209-2 (2003) • Case report • Accidental interruption of drug delivery is a common cause of awareness during general anesthesia • A rapid change of AEP was noted when infusion of anesthetics was stopped Liu, Chih-Min

  19. Prevention and Management of Awareness Liu, Chih-Min

  20. Conclusions • Incidence in general anesthesia: 0.1-0.2% • Incidence in cardiac surgery: 0.3% • Lower dose of anesthetics are associated with higher incidence of intra-op awareness; insufficient concentration • Standard physiologic monitoring is not reliable, such as AEP or BIS; however, clinical signs are much more unreliable • Psychiatric after-effect of awareness range from no effect to PTSD Liu, Chih-Min

  21. Conclusions • There is no evidence that any kind of premedication would affect the incidence of awareness • If prolonged laryngoscopy is required, one should not forget to add the induction agents or inhalation agent • In critical hemodynamic situation, BZD instead of general anesthetics may be acceptable • NMBs should be used as sparingly as possible • If the patient has a history of awareness under anesthesia, it would be wise to use monitor • If the patient has suffered from awareness, psychiatric consultation and follow-up is recommended. Liu, Chih-Min

  22. Discussion • Structured post-operative interviews • Best method • however • Large number of patients • Very sick patients: difficult to interview • Feedback information to the anesthesiologists • Education • Incidence from 4% to 1.5% in one study • Changes in drugs dosage • Increase in volatile agents, I.V. anesthetic agents • Decrease in muscle relaxant • BZD? • Have effect on memory but are not likely to be anesthetic Liu, Chih-Min

  23. Thanks for your attention! Liu, Chih-Min

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